A128556 a(1)=1. a(n) = the smallest positive multiple of d(a(n-1)) that does not occur earlier in the sequence, where d(m) is the number of positive divisors of m.

1, 2, 4, 3, 6, 8, 12, 18, 24, 16, 5, 10, 20, 30, 32, 36, 9, 15, 28, 42, 40, 48, 50, 54, 56, 64, 7, 14, 44, 60, 72, 84, 96, 108, 120, 80, 70, 88, 104, 112, 90, 132, 144, 45, 66, 128, 136, 152, 160, 156, 168, 176, 100, 27, 52, 78, 184, 192, 98, 102, 200, 180

Offset

1,2

Comments

Is this sequence is a permutation of the positive integers?

Links

Diana Mecum, Table of n, a(n) for n = 1..1000

Example

a(9) = 24 has 8 positive divisors. So a(10) is the smallest positive multiple of 8 that has yet to appear in the sequence. 8 occurs among the first 9 terms of the sequence, but 16 does not. So a(10) = 16.

Crossrefs

Cf. A128555.

Sequence in context: A114107 A362041 A175334 * A212485 A077661 A077583

Adjacent sequences: A128553 A128554 A128555 * A128557 A128558 A128559

Keyword

nonn

Author

Leroy Quet, Mar 10 2007

Extensions

More terms from Diana L. Mecum, May 29 2007

Status

approved